flex - File Upload with Adobe Air -

i'm trying upload file flex minus.com

the api reference explain upload example:

post /api/v2/folders/0fqhjakl/files?bearer_token=[token] http/1.1 host: minus.com content-type: multipart/form-data; boundary=----webkitformboundaryxecy8varbqixzw4f accept-charset: utf-8,*;q=0.5

------webkitformboundaryayaohdwfizxzb8oe content-disposition: form-data; name="file"; filename="test.txt" content-type: text/plain

test ------webkitformboundaryayaohdwfizxzb8oe content-disposition: form-data; name="filename"

test.txt ------webkitformboundaryayaohdwfizxzb8oe content-disposition: form-data; name="caption"

testfile ------webkitformboundaryayaohdwfizxzb8oe--

my as3 code is:

var params:urlvariables = new urlvariables();  params.caption = object.offlinefiles[0].name; params.filename = object.offlinefiles[0].name;  params.bearer_token=appmodel.logindata.access_token;  var fr:file = (object.offlinefiles[0] file);  fr.addeventlistener(ioerrorevent.io_error,uploaderror_handler);  var request:urlrequest = new urlrequest("http://minus.com/api/v2/folders/......./files"); request.data = params; request.method = urlrequestmethod.post;      fr.upload(request,"file"); 

but ioerrorevent...

try send "multipart/form-data".

var header:urlrequestheader = new urlrequestheader("enctype", "multipart/form-data"); request.requestheaders.push(header);